The overarching goal of our research program is to facilitate the development small-molecule drugs. The focus of this study is to explore the therapeutic potential of the cyclic dinucleotide class of immunopotentiators in cancer. Cancer is the second leading cause of death, contributing to 22.5% of total deaths in the US. Recently, immune checkpoint blockade has emerged as a powerful treatment modality for cancer, showing remarkable efficacy and response rate. Unlike the traditional radiation or chemotherapies, it utilizes our bodies? own immune system to fight cancer. However, many patients do not have sufficient immunity to benefit from this new treatment strategy. Our team has recently identified cGAMP to be the endogenous small-molecule that activates the innate immune system and demonstrated its antitumor activity in mice. Based on this work, several synthetic analogs have been developed by pharmaceutical companies to mimic this natural immunopotentiator. The accumulated effort has led to two Phase I clinical trials to evaluate the safety and tolerance of cGAMP analogs in human. Despite the rapid progress, the full functional profile of cGAMP is still not clear. In this project, we will establish a proteomic approach to extensively map drug-protein interactions for cGAMP and its metabolically stable analogs including the investigational drug MIW815. This work will help shed lights on the potential new functions of cGAMP and the potential off-target effects of synthetic cyclic dinucleotides. Additionally, we believe that selective activation of a specific group of dendritic cells by cGAMP or its analogs will help reduce the risk of systemic inflammation, the major concern of the immune stimulation therapies. We will thus develop a conjugation strategy for site-specific delivery of cGAMP to improve efficacy, reduce toxicity, and help understand the roles of dendritic cells at different sites in anticancer immunity. Overall, the results of this study will inform future development of cGAMP analogs for their safe use in human and provide information on the role of innate immunity in cancer.